Why Are Powders Complex?

The Influence of Particle Properties

In addition to the external variables described previously, there are a number of particle properties that contribute to powder flowability and bulk powder behaviour.
Particles are complex, yet never described by an adequate set of parameters in terms of their specification. Particle size and size distribution have traditionally been considered, and they remain important, but in fact there are many particle properties that will influence the overall behaviour of the powder.
Important particle properties include: -

Size

Shape

Surface Texture

Surface Area

Density

Cohesion

Adhesion

Elasticity

Plasticity

Porosity

Hygroscopicity

Hardness / Friability

Amorphous Content

Potential for Electrostatic Charge

Note that many of these properties are also distributions, rather than a single value.

Some properties can be measured directly, whilst others are more challenging to quantify. However, all have the potential to contribute to the way the powder behaves.

When considering the number and diversity of particle properties and external variables, it becomes clear why a mathematical and fundamental approach to predicting powder behaviour is very difficult,
if not beyond our current capability.